This invention relates to video graphic simulator systems, that is to say systems in which video signals are generated capable of producing an image on a television receiver, the signal being, however, generated or processed electronically with the aid of digital processing circuits.
A known form of such a system comprises a source of video signals representing a scene in which an object is movable. The scene may for example be generated using a system such as described in co-pending UK Patent Application No. 8136539. The source of these signals may be one or more frame stores. In addition there is a source of signals representing the object, the source being again, for example, a frame store. The object is associated with so-called stencil signals, one for each picture point for which there is an object signal, the stencil signals being usable to substitute the object signals for scene signals at the respective picture points, so that the object may be introduced in the scene. Furthermore, a computer or other control device is provided for scrolling the object signals and the associated stencil signals in some pre-determined way to represent movement of the object with respect to the scene.